The invention relates to an X-ray apparatus, comprising                an electron beam source, emitting an electron beam,        a target, onto which the electron beam is directed, thus forming a focal spot on the target,        X-ray optics, collecting X-rays emitted from the focal spot and forming an X-ray beam,        and a sample position at which the X-ray beam is directed.        
Such an X-ray apparatus is known from U.S. Pat. No. 7,929,667 B1.
By means of X-rays, samples may be investigated in a destruction-free and efficient manner. X-rays may interact with a sample in numerous ways in order to obtain analytical information about the sample, with X-ray diffraction (XRD) and X-ray fluorescence (XRF) being two important methods. In general, high X-ray intensities are useful to obtain high signal to noise ratios in X-ray analysis experiments.
X-rays are typically generated by directing an electron beam onto a target. The deceleration of the beam electrons (resulting in Bremsstrahlung) as well as the refilling of depleted deep electron shells of the target material (resulting in characteristic X-rays) leads to X-ray emissions within the focal spot of the electron beam on the target. In order to provide X-rays of a particular wavelength, monochromators may be used. Further, if the sample is significantly spaced apart from the focal spot, it is useful to focus X-rays by suitable optics such as Göbel mirrors or Montel optics.
U.S. Pat. No. 6,249,566 B1 proposes to combine a microfocus X-ray source with Montel type optics to focus X-rays onto a sample. Apparent focal spot sizes of about 30 μm or less are proposed.
A particular high brightness X-ray source has been proposed in U.S. Pat. No. 7,929,667 B1, wherein an electron beam is focused on a jet of liquid metal, such as gallium. Higher power loads on the target due to the electron beam and thus high brightness levels are possible as the target is already liquid and can dissipate quickly the generated heat from the focal spot. A multilayer X-ray focusing element may be used to shape an X-ray beam. Focal spot sizes of about 10-15 μm are mentioned.
U.S. Pat. No. 6,711,233 B2 also proposes an X-ray source wherein an electron beam is directed onto a liquid metal jet target. It is proposed to match the size of the electron beam with the size of the jet, with the jet having a diameter of about 1-100 μM.
When combining a microfocus X-ray source with X-ray optics, it is necessary to align these components with respect to each other. Alignment in this sense means that a certain aspect of the beam properties downstream the mirror is maximized. Depending on the aimed application this aspects can for example be flux density or integral flux. In classical x-ray systems this is achieved by changing the x-ray optics and mechanically repositioning the x-ray optics. However, mechanically moving the X-ray optics on the μm range to match the focal spot of the X-ray source with the focus of the X-ray optics is difficult in practice, in particular due to backlash of alignment mechanics.
It is the object of the invention to provide an X-ray apparatus wherein aligning the X-ray optics with respect to a microfocus X-ray source is simplified.